The invention relates to improved hook members for hook-and-loop fastening and methods of manufacturing hook members.
In general, hook-and-loop fasteners comprise two mating components: a hook member that has upstanding, hook-type fastener elements, and a loop member that has a surface that provides fibers or fiber loops with which the hook elements become engaged.
As used here, a xe2x80x9chook memberxe2x80x9d means a member having fastener elements whose hooks extend substantially in a given plane. When of molded form, the stems of these elements are significantly broader in the direction of their plane of extent than in the thickness direction at a right angle thereto.
Hook fasteners are often preferred over other types of fasteners, for instance, those having mushroom-like form, because hook fasteners can provide more secure engagement with the loops, offer advantages in manufacturing, etc.
Loop members for hook-and-loop fastening have been comprised of knitted, woven, and non-woven textiles. A common example of a non-woven textile is known by the term xe2x80x9cspun bondedxe2x80x9d. It is made by spinning fine filaments of plastic resin, e.g., polypropylene, and distributing them in superposed layers. The fibers are bonded to each other in random orientations, with a fine, low-lying, nappy layer of looped and arched fibers exposed at the surface of the fabric.
Because non-woven fabrics are inexpensive, they are desired for use as the loop part of fasteners for low cost items, particularly disposable products such as diapers, surgical gowns, and sanitary napkins. It is desirable to provide fastener members useful with very low cost, low loft non-wovens and other low loft fabrics.
One aspect of the invention relates to a fastener member useful for separable engagement with surface fibers of a low-loft, non-woven fabric or the like. The fastener includes a base and multiple rows of molded hook-form fastener elements extending from the base and exposed for engagement with the fabric. Each of the hook form fastener elements comprises a stem portion joined at one end to the base and at least one fiber-engaging hook-form portion joined at the opposite end of the stem portion and having a free end. The hook-form fastener elements lying substantially only in planes aligned with respective rows. At least some of the fastener elements include a fiber-engaging plate portion at the outermost portion of the hook-form portion, which plate portion lies generally parallel to the base. The plate portion provides an overhanging portion in the direction perpendicular to its row that can engage the surface fibers of the fabric.
Certain implementations of this aspect of the invention include one or more of the following features. The fastener member, in certain implementations, provides: a plate portion which has a thickness, in the direction normal to the base, that is less than the height, in the direction normal to the base, of the free end of the hook portion; fastener elements formed of thermoplastic resin, the stem portions of the elements being molded integrally with the base, and the plate portion comprising a post-formed structure formed from the resin of the uppermost portion of the molded fastener element; that substantially all the hook-form portions of the fastener elements in a first row extend in one direction along the row and substantially all the hook-form portions of the fastener elements in a neighboring second row extend in the opposite direction; that substantially all of the fastener elements include plate portions; that substantially all of the fastener elements in the first row contain a plate portion while substantially all of the elements in the neighboring second row do not; a stem portion which has substantially flat relatively broad sides, a cross-section of each stem portion, taken parallel to the base at the mid-height region of the stem, having a width in the direction of the row and a thickness in the direction perpendicular to the row, the width being about twice the thickness or more; a stem in which the width of the stem tapers from the base to the hook-form portion; a central axis of the stem is inclined, in the direction of the respective row, at a substantially acute angle relative to the base.
Another aspect of the invention relates to a fastener member useful for separable engagement with surface fibers of a low-loft, non-woven fabric or the like. The fastener comprises a base and multiple rows of molded fastener elements extending from the base. Each fastener element comprises a stem portion joined at one end to the base, the stem being inclined, at a substantially acute angle relative to the base in the direction of the respective row of the element, and lying substantially only in planes aligned with its respective row relative to the base, and a fiber-engaging plate portion disposed at the opposite, outermost end of the stem portion, the plate portion extending transversely to the direction of the respective row to form an overhang portion that can engage the surface fibers of the fabric.
Certain implementations of this aspect of the invention include one or more of the following features. The fastener member, in certain implementations, provides a cross-section of each stem portion, taken parallel to the base, has a width in the direction of the row and a thickness in the direction perpendicular to the row, the width being substantially greater than the thickness; that substantially all of the fastener elements include plate portions.
In accord with another implementation of the invention, a closure is provided comprising a fastener member as described above and a non-woven fabric engaged therewith, the base of the fastener and the non-woven fabric being under tension in opposite directions such that the fastener elements are subjected to and resist shear forces caused by the tension loading, the tension acting in the direction of the thickness of the stem portion.
Another aspect of the invention relates to a method for making fastener members comprising extruding molten resin and applying the resin to a molding roller having forming cavities around its perimeter. Pressure is applied to the resin to cause the resin to fill the cavities, thereby forming a fastener member preform, the fastener member preform comprising a base and a multiplicity of discrete fastener element preforms integrally molded with and extending from the base at a substantially acute angle, the fastener element preforms aligned in at least one row comprising stem portions with outermost ends lying over the base substantially only in planes aligned with its row. Fastener member preforms are stripped from the molding roller. The outermost portions of at least some of the fastener element preforms are flattened, thereby forming generally plate-shaped portions disposed at the outermost ends and generally parallel to the base and perpendicular to the row.
Certain implementations of this aspect of the invention include one or more of the following features. The method, in certain implementations, provides: the flattening comprises heating the outermost ends of at least some of the fastener element preforms to a temperature that is near the melt temperature of the resin and applying pressure to the outermost ends; the heating and the applying pressure are performed in a single step; the single step comprises passing the fastener member preforms by a heated roller and pressing at least some of the fastener element preforms against the heated roller; the fastener member preforms are formed and the outermost ends of at least some of the preforms are flattened as part of a single, continuous process; the outermost ends of at least some of the fastener element preforms are flattened in a post-processing operation; prior to the flattening, differences in the heights of the fastener element preforms are corrected to ensure generally uniform height; the correcting comprises pressing a knock-down roller against the outermost ends of the fastener element preforms; that substantially all of the fastener elements are flattened; that a product is formed by the method.
In another aspect of the invention, the outermost portions of some fastener elements are farther away from the base, as formed, than the outermost portion of at least some other fastener elements. At least some of the outermost portions farthest away from the base are then flattened, forming generally plate-shaped portions disposed at said outermost ends and generally parallel to the base and perpendicular to the row.
In a preferred embodiment, stripping the preforms from the molding roller causes the fastener members extending in one direction to be deformed to be of greater height than fastener members in another direction.
Another aspect of the invention relates to a method for improving the engageability of a hook-type fastener member with a non-woven loop-type fastener member. The hook-type fastening member comprising a base and a multiplicity of generally hook-shaped fastener elements integrally molded with and extending from the base in a given direction or in that direction and the opposite direction and lying only in planes parallel with the given direction and perpendicular to the base. The method comprises flattening outermost ends of at least some of the fastener elements to form generally plate-form portions disposed at the distal ends and generally parallel to the base and perpendicular to the planes.
The new hook fastener members are well suited for engagement with low loft non-woven loop members since the outer plate portions of the fastener elements that overhang the sides of the elements are able to slide under and initially engage the surface fibers of the loop member. This feature can improve the level of engagement of the fastener, especially when the fastener elements are subjected to shear forces acting sideways relative to the direction of the plane of the hook elements. The flat-top hook fastener elements, while providing the secure engagement by the hooks, also can avoid skin irritation since the area of contact between the skin and the fastener elements is relatively large. This is of particular value when a hook fastener comes in contact with the skin of babies. Finally, these hook fasteners can be manufactured using conventional hook-member tooling with simple additional post-molding steps.
Other aspects of the invention concern a disposable absorbent garment having first and second opposed longitudinal end portions, and comprises an outer cover; a body-side liner; an absorbent core located between the outer cover and the body-side liner; a loop member operably associated with the garment; and a fastener member operably associated with the garment for separable engagement with the loop member, the fastener member comprising: a base; and multiple rows of molded hook-form fastener elements extending from the base.
According to one aspect of the invention, the fastener elements are exposed for engagement with the loop member, each of the hook-form fastener elements comprising a stem portion joined at one end to the base and at least one fiber-engaging hook-form portion joined at the opposite end of the stem portion and having a free end, the hook-form fastener elements lying substantially only in planes aligned with respective rows. At least some of the fastener elements include a fiber-engaging plate portion at the outer most portion of the hook-form portion, the plate portion lying generally parallel to the base, the plate portion providing an overhang portion in the direction perpendicular to its row.
Certain implementations of this aspect of the invention have one or more of the following features.
The plate portion has a thickness, in the direction normal to the base, that is less that the height, in the direction normal to the base, of the free end of the hook portion. The stem portion has substantially flat relatively broad sides, a cross-section of each stem portion, taken parallel to the base at the mid-height region of the stem, having a width in the direction of the row, and a thickness in the direction perpendicular to the row, the width being about twice the thickness or more.
Certain advantageous implementations of this aspect of the invention have one or more of the following features. The loop member comprises a nonwoven material. The loop member is joined to the outer cover in the first opposed longitudinal end section and the fastener member is operably associated with the second opposed longitudinal end section, preferably the garment 25 having a longitudinal axis and wherein the fastener elements are oriented parallel to the longitudinal axis of the garment.
According to another aspect of the invention concerning the disposable absorbent garment, each of the fastener elements comprise a stem portion joined at one end to the base, the stem being inclined at a substantially acute angle relative to the base, in the direction of the respective row of the fastener element and lying substantially only in planes aligned with its respective row. At least some of the elements also comprise a fiber-engaging plate portion disposed at the opposite, outermost end of the stem portion, the plate portion extending transversely to the direction of the respective row to form an overhang portion.
In preferred embodiments of the aspect of the invention, a cross-section of each stem portion, taken parallel to the base, has a width in the direction of the row and a thickness in the direction perpendicular to the row, the width being substantially greater than the thickness.
Certain advantageous implementation of both of these aspects of the invention include that substantially all of the fastener elements include plate portions.